# std::basic_stringbuf<CharT,Traits,Allocator>::seekpos

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< cpp‎ | io‎ | basic stringbuf

protected: virtual pos_type seekpos( pos_type sp, std::ios_base::openmode which = std::ios_base::in | std::ios_base::out ); |  |

Repositions std::basic_streambuf::gptr and/or std::basic_streambuf::pptr, if possible, to the position indicated by sp.

Effectively executes seekoff(off_type(sp), std::ios_base::beg, which).

### Parameters

sp | - | stream position, such as one obtained by seekoff() or `seekpos()`
which | - | defines whether the input sequences, the output sequence, or both are affected. It can be one or a combination of the following constants:
Constant | Explanation
`in` | affect the input sequence
`out` | affect the output sequence

### Return value

sp on success or pos_type(off_type(-1)) on failure.

### Notes

`seekpos()` is called by std::basic_streambuf::pubseekpos(), which is called by the single-argument versions of std::basic_istream::seekg() and std::basic_ostream::seekp().

### Example

Run this code

    #include <sstream>
    #include <iostream>

    struct mybuf : std::stringbuf
    {
        mybuf(const std::string& str) : std::stringbuf(str) {}

        pos_type seekpos(pos_type sp, std::ios_base::openmode which)
        {
            std::cout << "Before seekpos(" << sp << "), size of the get area is "
                      << egptr() - eback() << " with "
                      << egptr() - gptr() << " read positions available.\n";

            pos_type rc = std::stringbuf::seekpos(sp, which);

            std::cout << "seekpos() returns " << rc << ".\nAfter the call, "
                      << "size of the get area is "
                      << egptr() - eback() << " with "
                      << egptr() - gptr() << " read positions available.\n";

            return rc;
        }
    };

    int main()
    {
        mybuf buf("12345");
        std::iostream stream(&buf);
        stream.seekg(2);
    }

Output:

    Before seekpos(2), size of the get area is 5 with 5 read positions available.
    seekpos() returns 2.
    After the call, size of the get area is 5 with 3 read positions available.

### Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR | Applied to | Behavior as published | Correct behavior
--- | --- | --- | ---
LWG 375 | C++98 | static constant members of std::ios_base were misspecified as members of std::basic_ios | corrected
LWG 564 | C++98 | if was unclear how to reposition `gptr` and/or `pptr` | they are repositioned by seekoff()

### See also

pubseekpos | invokes seekpos() (public member function of `std::basic_streambuf<CharT,Traits>`)
seekoff [virtual] | repositions the next pointer in the input sequence, output sequence, or both, using relative addressing (virtual protected member function)
seekpos [virtual] | repositions the file position, using absolute addressing (virtual protected member function of `std::basic_filebuf<CharT,Traits>`)
seekpos [virtual] | repositions the next pointer in the input sequence, output sequence, or both using absolute addressing (virtual protected member function of `std::strstreambuf`)

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